at a gas station
No applications in the real life; francium is only an object of studies in specialized research laboratories.
You reading this answer.
In my openion bubbles in the soap film is the real examples of it.
Carin and machines
a sponge
its not.
An example of a real world rate is 45630.19106 debt per capita (person).
How fast you can run is a rate which applies only to you.
determing current flow in ammeters
The flow of an ideal fluid through a tube is a quartic function -- the flow rate varies with the radius to the 4th degree. So if you double the radius of a tube, 16 times more fluid can pass through the tube in the same interval of time.
a roller coaster. It doesnt have a constaant rate of change
plant growth, stocks, bank account balances, temperature...
Conventional current flow refers to a flow of positive charges. It is a kind of ficticious current. If - as is often the case - the real current is an electron flow (negative charges), then the conventional flow is a current in the opposite direction as the electron movements, since this would have the same effect (for example on the magnetic field, or on conservation of charge).
A real interest rate and a nominal interest rate are quite similar. The only real difference between the two interest rates are that a nominal interest rate include the cost of inflation where as the real interest rate does not.
Some examples: Your velocity is the rate of change of distance (even if you don't think of it in that way). Your acceleration is the rate of change of velocity. Your pay rise is the rate of change of your pay (per year).
Difference between real and nominal cash flow is that nominal cash flows uses the inflation information as well for calculation of nominal cash flow of future while real cash flow don't use that information for calculation.
The perfect-use rate is the same for all ages. The real-life effectiveness rate is lower in teens because they don't return for reinjection on schedule.